1. Field of the Invention
This case relates to the downhole evaluation of solid materials using terahertz spectroscopy. More particularly, this case relates to downhole apparatus and methods for evaluating or characterizing compositional analysis of solid material such as formation cores or such as scale deposits in a wellbore, although it is not limited thereto.
2. State of the Art
Precise and real-time information is desirable for optimal evaluation and development of oil-gas-water reservoirs. The evaluation of the formation properties is a major factor in dictating reservoir development strategies including well design and production methods, and can ultimately impact recovery factors. Real-time data (obtained downhole) about the formation and the formation fluids are a valuable source of information during reservoir evaluation.
One aspect of formation characterization relates to the geological makeup of the formation. While formation samples (e.g., cores) can be obtained downhole and brought uphole for evaluation at a surface laboratory to obtain data, in some cases the delay can result in well-development mistakes that could have been avoided or predicted had real-time data been available.
Another aspect of the evaluation and development of oil-gas-water reservoirs relates to the flow of fluid in the formation, borehole or completed wellbore. By way of example only, it is not uncommon in a reservoir that barium may have slowly leached over geological time so that it is present in aqueous solution. This situation is stable until sulfate rich seawater is injected into the formation for production purposes. A chemical reaction then occurs and produces an unstable super-saturated barium-sulfate solution that will start to crystallize (i.e., form scale) with only small changes in temperature or pressure. Conditions for scale deposition can occur in one or more of the formation itself, the perforation tunnel of the casing, the wellbore or the tubing (pipe). A buildup of scale can significantly impact production. Because barium-sulfate is not radioactive, a gamma ray logging tool cannot detect the barium-sulfate scale. Likewise, while a calipers tool can detect the build-up of scale in the wellbore or tubing, it cannot determine the composition of the scale deposit.